The metabolism and permeability of erythrocytes obtained from Duchenne (DMD) and myotonic muscular dystrophy (MMD) patients will be investigated in incubation experiments conducted in vitro. The premise underlying these studies is that the changes observed in erythrocytes may reflect alterations that are present in the muscles of these patients, since these myopathies are believed to be genetically-transmitted diseases involving cell membranes of various cell types. In order to account for an earlier observation that total phosphorous concentration in erythrocytes from male MMD patients is lower than in controls, it is proposed that anion permeability may be altered. Radiosulfate influx and efflux will therefore be evaluated. Since the altered permeability might be related to an altered phospholipid metabolism, the influence of added lysophosphatidylcholine (LPC), dipyridamol, and prachloromercuribenzoate sulfonate and sulfate permeability will be examined. LDC concentrations that cause lysis in MMD, DMD, and control erythrocytes will also be determined. Phospholipase and lysophospholipase activites will be assessed in membrane preparations from MMD, DMD, and control erythrocytes.